Multi Topology Routing Truman Boyes

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Lucas Arnold
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3 Overview This is not an alternative to MPLS. There is much confusion on MTR and where it best fits. MTR divides a network into multiple logical groups. It provides isolation but not VPNs. MTR creates multiple RIB / FIB combinations in addition to the base routing context. Topologies can be shared or separate. N dimensional vectors of different costs for each link in the network Copyright 2008 Juniper Networks, Inc. 3

5 MPLS + IP TE You already have an MPLS Network. You want to carry IPv4 Internet traffic inside your global default routing instance. You don t want Internet traffic to traverse some links in your network. Copyright 2008 Juniper Networks, Inc. 5

6 IPv6 video traffic MTR You carry IPv4 and IPv6 routes in your default routing context. You use OSPF to populate the respective RIBs. You want IPv6 video traffic to use specific links. You want IPv6 data traffic to use any link. Copyright 2008 Juniper Networks, Inc. 6

7 Wholesale / Reseller MTR Specific prefixes / Interfaces are mapped into topology contexts. (ie. Wholesale). Wholesale context is engineered to stay on specific technologies (Ethernet) and specific nodes. Wholesale links use different queuing characteristics and may not have MPLS FRR. Copyright 2008 Juniper Networks, Inc. 7

8 ISP with MPLS LSPs for EF traffic, but BE should use IP Next Hops ISP may not want a lot of MPLS encap overhead for high volume BE traffic. MPLS is used in strategic location to provide FRR and VPNs to Business Traffic. Many IP Only Routers in the Network. By default JUNOS will prefer LSPs instead of IP Next Hops. This concept can be achieved with MTR implementation. Copyright 2008 Juniper Networks, Inc. 8

9 Non Congruent Inter domain Topologies Autonomous System may want to receive VoIP on a given prefix on one link (due to latency) and all other data for the same prefix on another link. Could be solved with policy and MTR. Alternatives could be multiple LSPs with classbased forwarding policy, and Inter AS VPNs. This may be more complex Copyright 2008 Juniper Networks, Inc. 9

11 On a single router: multiple topologies RIB/FIB The default topology is populated from the IGP and BGP. Wholesale topology Default Topology Voice topology Video topology Biz topology RIB/FIB RIB/FIB RIB/FIB Individual topologies are created, which contain their own RIB / FIB. Firewall policies / Classifiers are created to place traffic into the appropriate FIB. Routing protocols (OSPF, BGP, static) supported. Copyright 2008 Juniper Networks, Inc. 11

12 Not Quite a Standard OSPF MT (RFC 4915) Copy MT ID into ToS field (32 127) BGP MTR No RFC JUNOS uses community values for each topology ID. Each route is installed into default RIB & topology RIB. Route target Community based, not a new SAFI. IOS version uses BGP session per topology. This does not require a new protocol extension. ISIS MT (RFC 5120): new TLV. Reserved MT IDs for IPv4 and IPv6 routing topology. Copyright 2008 Juniper Networks, Inc. 12

15 Constructs Topology RIB/FIB creations. (ie. Define the topology names you want). Do this on all routers. Enable MT extensions on IGP OSPF MT IDs Enable BGP topology / route control ibgp routes inside a topology context will use the respective OSPF/ISIS context for next hop route resolution. Modify forwarding plane with firewall filters to place the respective traffic into each topology FIB. Copyright 2008 Juniper Networks, Inc. 15

16 OSPF MT details ToS Field redefined as MT ID MT Area Boundary Each OSPF interface belongs to a single area and all MT s sharing the link must belong to the same area. Adjacencies Single adjacency even if there are multiple topologies. LSAs Router / Summary / Type 5 and Type 7 AS External LSAs are modified to contain MT ID. No change to Network LSA. DR is shared by all topologies. Copyright 2008 Juniper Networks, Inc. 16

17 More OSPF MT Details Separate SPF calculation for each topology. Max metric can be used, but OSPF doesn t have concept of unreachable link. There is a new concept with MT, where links can be excluded (in the spec) from the default MT ID #0 topology. MT bit is in Hello packet Copyright 2008 Juniper Networks, Inc. 17

18 Migrating non MT Areas to MT Areas If you need to exclude links from the default topology, all routers in the area must support DefaultExclusionCapability. MT Area routers will interact with non MT Area routers in the default topology. Upgrading the backbone area first is desirable. Gradually you can upgrade the entire area to MT. Copyright 2008 Juniper Networks, Inc. 18

19 Ideas Management Topology RIB Video Dual Head Feeds over 2 paths Prevent additional overhead on some networks Offline TE metric calculations for OSPF MT Integration with Event/Commit/Op Scripts for Automatic behaviour. XML RPC/NetCONF reconfigurations of metrics on IP networks. Using Overload Bits per Topology! Awesome way to redirect traffic when working on a service. Advertising LSPs into OSPF MT Copyright 2008 Juniper Networks, Inc. 19

20 A bit about BGP Multi Topologies 3 approaches Community based Multi Session New AFI/SAFI Community based approach is better on memory, but is more limited. Communities might make sense between border routers, but beyond that they don t work well between AS if the same prefix is advertised with different topologies. Copyright 2008 Juniper Networks, Inc. 20

21 Summary Another tool to add to the tool belt. Relatively easy to setup in IP networks. Integrates with MPLS networks. There are multiple ways to match traffic. BA or Firewall Terms Troubleshooting with standard tools Ping / Traceroute / Tcpdump Available Now Copyright 2008 Juniper Networks, Inc. 21

23 Configurations [edit protocols ospf] topology (default ipv4 multicast name) { topology id number; spf options { delay milliseconds; holddown milliseconds; rapid runs number; interface interface name { metric metric; topology (ipv4 multicast name); metric metric; Copyright 2008 Juniper Networks, Inc. 23

25 JUNOS MTR with BGP group ebgp { type external; local address ; family inet { unicast { topology voice { community target:40:40; topology video { community target:40:40; peer as 101; neighbor ; Copyright 2008 Juniper Networks, Inc. 25

26 MTR and the Forwarding Table firewall { family inet { filter ef_path { term ef { from { forwarding class expedited forwarding; Filter on DSCP then topology voice; term video { from { source address { Filter on address /24; /24; /24; /24; then Topology video; term default { then accept; Copyright 2008 Juniper Networks, Inc. 26

27 IOS Snippets Router(config router af)# topology VOICE tid 10 router bgp <autonomous system number>! Global commands scope {global vrf <vrf name>! Scoped commands address family {<afi> [<safi>]! Address family specific commands topology {<topology name> base! Topology specific commands Copyright 2008 Juniper Networks, Inc. 27

28 More IOS Snippets global address family ipv4 topology VOIP all interfaces exit topology HDTV forward base maximum routes exit exit class map match any VOIP match ip dscp 9 exit class map match any HDTV match ip dscp af11 exit policy map type class routing ipv4 unicast MTR class VOIP select topology VOIP exit class HDTV select topology HDTV exit exit global address family ipv4 service policy type class routing MTR end Copyright 2008 Juniper Networks, Inc. 28

29 Specific Route Resolution routing options { autonomous system 65300; resolution { rib inet.0 { resolution ribs inet.0; rib :voice.inet.0 { resolution ribs [ inet.3 :voice.inet.0 ]; topologies { family inet { topology voice; Copyright 2008 Juniper Networks, Inc. 29

MPLS VPN--Inter-AS Option AB

MPLS VPN--Inter-AS Option AB The feature combines the best functionality of an Inter-AS Option (10) A and Inter-AS Option (10) B network to allow a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) service provider